The overall goal of this project is to determine what factors affect the risk of recurrence and death in women diagnosed with breast cancer before age 45. This project builds on the information already collected on 1400 women who were diagnosed with invasive breast cancer before age 45 from 1983 - 1992 and interviewed about risk factors for disease. This cohort will be followed for recurrence and mortality through December, 1996. These women represent the majority (85%) of incident cases from these years in King, Pierce, and Snohomish Counties in Washington State. From within this cohort, all women with recurrence and/or death will be identified. These women will be compared to women from within the cohort without recurrence and/or death on the following factors: 1. Patient characteristics and risk factors collected in the detailed interview such as oral contraceptive use, history of induced abortion, and other reproductive factors, family history of breast cancer, mammography history, obesity, etc. 2. Timing of surgery in relation to the menstrual cycle. 3. Histopathologic characteristics including histologic type, generalized nuclear grade, number of mitoses, size, multicentricity, location, clinical presentation, lymph node metastases, and status of margins of the tumors as determined by pathologic review. 4. Expression of tumor-related proteins by immunocytochemistry, including steroid receptors, oncogene proteins, p53 tumor suppressor gene product, growth factors, and proliferating cell nuclear antigen (PCNA). 5. Evidence of angiogenic response determined by image analysis quantification of vascular density and mRNA expression of angiogenesis-related factors. 6. Cell proliferation and aneuploidy determined by flow cytometric analysis of S-phase fraction and DNA content of formalin-fixed, paraffin-embedded tumor. In addition, we will evaluate the relationship(s) of patient characteristics and exposure data (1 and 2 above) to tumor characteristics (3 - 6 above) at diagnosis.